1. Field of the Invention
The present invention relates to surgical devices for repair of split portions of tissue. In particular, the invention is directed to a strap assembly for securing a strap about split portions of a sternum to maintain the portions in adjacent contacting relation during healing.
2. Description of the Prior Art
During surgery that involves a median sternotomy, e.g., open heart surgery, the sternum is split longitudinally to permit access to the organs within the thoracic cavity. Upon completion of the surgery, the sternum is rejoined and closed securely. For proper healing to occur, the split sternum portions are preferably engaged in a face-to-face relationship and compressed together while the sternum heals.
Traditional methods for closing a sternum involve securing steel wires around or through the sternum halves and approximating the sternum by twisting the wires together.
Recently, a certain amount of emphasis has been directed towards the use of band or strap assemblies for sternum repair. Such assemblies typically include a locking mechanism which secures a strap in a closed looped configuration about the sternum portions. One example of an assembly of this type is described in U.S. Pat. No. 4,813,416 to Pollak et al. and includes a banding assembly having a curved surgical needle, an attached thin flat stainless steel band and a buckle mechanism. The sternum halves are brought to abutting closure by looping the band in position around or through the sternum portions and securing the band within the buckle mechanism.
Another example of a device contemplated for use in sternum closure is described in U.S. Pat. No. 4,730,615 to Sutherland. The Sutherland '615 device includes a head portion having a locking tang and a spine portion extending from the head portion. The spine portion is made of a biocompatible metal coated with a biocompatible polymer and possesses serrations along part of its length. In use, the spine portion is wrapped about the sternum and introduced within the head portion. The tang pierces the polymer coating and locks against a serration of the spine.
While utilization of steel wires and strap assemblies have been widely accepted for sternum repair, certain shortcomings with these devices are apparent. The use of steel wires presents problems to the surgeon during the operation and to the patient after closure is completed. Steel wires are difficult to maneuver and place around the sternum. The wire edges are often shard and can easily pierce through undesired areas including tissue surrounding the sternum area or the surgeon's gloves or fingers.
The strap assemblies known heretofore incorporate buckle mechanisms which are relatively structurally complex. For example, the buckle mechanism described in U.S. Pat. No. 4,813,416 includes a saddle part, interned flanges disposed on opposed sides of the saddle part and a loop segment. The saddle part and interned flanges define a band slide through course for reception of a portion of the band. A spring leaf extends upwardly from the loop segment through a slot in the saddle part. The rid end of the spring leaf is narrowed to define a spring tooth or projection which projects through an aperture formed in the band to maintain the closed band loop in a locked configuration.
Another significant disadvantage with the strap assemblies known heretofore is that the locking devices are typically made of a non bioabsorbable material such as stainless steel. The metallic components therefore remain within the patient indefinitely after healing has occurred.
Thus, there is a clear need for a surgical device which is simple in construction and effectively secures the divided sternum portions together for healing in a less invasive manner than that of known assemblies. It is also preferable that such device be at least partially fabricated from bioabsorbable materials. The present invention is directed to a bioabsorbable strap assembly of relatively simple construction, which securely retains a strap in a closed looped locking configuration around sternum portions to maintain the portions in adjacent engaged relation during healing.